Question

What is the molar mass of $Pb{(S{O_4})_2}$? How is this value calculated?

Answer 1

We must always remember that Molar mass is different from the Molecular mass. Molar mass is also called the Molecular weight. Molar mass of the chemical compound is the mass of one mole of the compound.

Complete step by step answer:
First, what is a Molar mass? Molar mass, also called as the Molecular weight, is the mass of one mole of the substance. It is expressed in the units of $gmo{l^{ - 1}}$.
- We need to follow the following steps to calculate the molar mass.
- First, we have to identify the formula of a given compound or molecule.
- Then determine the number of moles of atoms present in the given compound or molecule.
- we have to Multiply the mass of each atom present in the compound with the number of moles of the atom.
- Do this for every element present in the compound.
- Finally add all these values.
- The obtained value is expressed in $gmo{l^{ - 1}}$.
Let us now move onto the given question. In the lead sulphate$Pb{(S{O_4})_2}$, there are one lead atom, two Sulphur atoms and eight oxygen atoms.
- Now we have to calculate the molar mass of $Pb{(S{O_4})_2}$.
Molar mass of $Pb{(S{O_4})_2}$ = Molar mass of lead + molar mass of sulphur + molar mass of oxygen.
Molar mass of $Pb{(S{O_4})_2}$ = $1 \times 207.2 + 2 \times 32.06 + 8 \times 15.99$
Molar mass of $Pb{(S{O_4})_2}$ = $399gmo{l^{ - 1}}$
Therefore, the molar mass of lead sulphate, $Pb{(S{O_4})_2}$ was found to be $399gmo{l^{ - 1}}$.

Note: We have to remember that molar mass and molecular mass are different from one another. Let us now see the comparison between the two:

MOLAR MASS	MOLECULAR MASS
Molar mass is said to be the mass of one mole of the substance.	Molecular mass is the mass of the molecule.
It is expressed in $gmo{l^{ - 1}}$.	It is expressed in amu.
It is also known as Molecular weight.	It determines the mass of a single molecule.